In the past few decades, there has been an increasing interest in using conducting polymers to fabricate electronic or optical devices such as light-emitting diodes and molecular electronics. Polyaniline (PANI) has been one of the most commonly used conducting polymers due to its facile synthesis, lower cost and environmental stability and has been carefully examined for use in electromagnetic shielding and anticorrosion coatings.
PANI possesses secondary and tertiary amines in the backbone structure that can bind metal ions. The metal ions can be released from the PANI by immersion of the PANI into a low pH solution. The ability of PANI to bind metal ions and to subsequently release them has made PANI an attractive material for environmental remediation. In cases where metal ions have a reduction potential higher than that of the PANI, the bound metal ions can be reduced to form zero-valent metals. Thus, it has been recognized that PANI can be used for the electrodeless precipitation of metals from a metal ion solution.
Reduction and precipitation of gold from acid-solutions using conducting polymers has been shown for the recovery of gold from solutions (Kang et al., Journal of Chemical Technology and Biotechnology, 1994, 59, 31-36). Metallization of printed circuit boards using PANI has also been shown (Huang et al., Molecular Crystals and Liquid Crystals, 1990, 189, 227-235).
Despite the prior work on deposition of metals using polyaniline, the nature of the metal structure, e.g., nanostructure, on the conducting polymer surface has not been controllable. The metals deposited in prior work are featureless, particularly at the nanoscale level, simply serving the purpose of being electrical conductors.